RFR(XXS) 8230363: C2: Let ConnectionGraph::not_global_escape(Node* n) return false if n is not in the CG

[Reingruber, Richard]

Hi,

could I please get reviews and sponsoring for

Webrev: http://cr.openjdk.java.net/~rrich/webrevs/2019/8230363/webrev.0/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8230363

The fix avoids crashes if ConnectionGraph::not_global_escape(Node* n) should be called with a node n
that was not added to the connection graph. Note that not all ideal nodes are added (e.g. constant
numbers). This case should be handled more gracefully by returning false.

This is split off from JDK-8227745[1]. There not_global_escape() is applied to the arguments of java
calls. If one argument should be e.g. an integer constant not_global_escape() would crash.

I've run tier1 tests.

Thanks, Richard.

[1] https://bugs.openjdk.java.net/browse/JDK-8227745